A. Field of Invention
This invention pertains to a system with a disc drive and a player. In one mode of operation, the two can be locked so that only discs having special characteristics, such was watermarks are played. Once unlocked, the disc driver and player can play other types of discs, such as data discs.
B. Description of the Prior Art
The use of audio and video watermarks in audio-visual works has been established as a practical means of inhibiting unauthorized distribution of commercial content (henceforth referred to as just “content”). A hidden mark is embedded in either the audio or the visual image of the work to be protected. The hidden mark typically has the following characteristics:    1. It does not impede enjoyment of the work. For example, a video watermark is “invisible” when viewed under normal viewing conditions.    2. It resists attempts to remove it. This is typically accomplished by technology that ensures that enjoyment of the work is substantially impaired if the mark is removed. For example, an audio watermark cannot be removed from the sound track of an audio visual work without serious degradation to the sound track.    3. It can carry data indicating, for example, the ownership of the work, the location in which it was created or the presence or absence of other watermarks on the disc.
A watermark system consists of two parts:    1. An embedding system.    2. A detection system.
The embedding system is usually integrated into the authoring process so that at some point prior to the work being replicated and/or distributed the mark is inserted. Embedding watermarks is a well-known practice. For example, if the work were to be distributed on a DVD-Video disc the mark would be embedded into the content after compression and before encryption with the content protection system. Optical discs are used as the primary example in this document but the invention described herein is equally applicable to many other means or media of content delivery.
The watermark system serves one of two specific purposes.
One purpose is for forensic tracking of content. In connection with such a purpose, content is marked with an individually tailored watermark code that represents some information relating to where or to whom the content is to be sent. For example, the mark might identify the particular vendor that was used for a part of the production process, the movie theatre that a film is sent to for projection, or a person to whom a “screener” copy of the work was sent to ahead of its release to normal distribution channels. In this case, the detection system is controlled by the content owner so that when content is found in unauthorized circumstances, it is possible to trace where and/or to whom the content was originally delivered. For example, a forensic mark in a motion picture found on a peer-to-peer network might indicate the identity of the person who legitimately received a screener copy of the motion picture.
The other purpose is for controlling playback and/or recording of content. Here content is marked with a well-known mark that is detected in real time or better in any device that renders (plays) or records the content. Here, the detection system is in the playback or recorder system and outside the control of the content owner.
For the purposes of this document we will mainly consider playback control, although much of this discussion applies equally to record control and should be understood as such. When watermarks are used for playback control the detection system must be activated when (or, preferably, before) the content is played. If the watermark is detected outside of the allowable usage then playback will stop, while if the watermark is detected within the allowable usage then playback will proceed. If the detection system is turned off or by-passed it cannot prevent the unauthorized playback of marked content. Some device (e.g. video disc players) manufacturers are reluctant to incorporate detection systems (or incorporate such systems which are easily bypassed via widely available input codes) since they perceive that they may be placed at a market disadvantage in relation to a competitor that does not incorporate the detection system. The detection system is intended to prevent the playback of unauthorized content. Therefore, devices that incorporate detection systems may be unattractive to consumers who are interested in viewing unauthorized content such as pirated DVD-Video discs that carry the watermark.
With respect to current systems, contractual obligations are often the key to the incorporation of detection systems in player and recorder devices. Typically a device manufacturer will need to obtain access to content protected by a particular content protection scheme, such as Content Scramble System (“CSS”), and will, as a result, accept a detection obligation in order to also obtain the needed access license.
The effectiveness of contractual obligations, however, varies. It depends on various factors such as the specific delivery method(s) covered. For example, in the case of optical discs, the contractual obligation may apply to all types of optical discs, or may be limited to just the types associated with the content protection system that requires the obligation as part of its license. The effectiveness of contractual obligations also depends on the implementation of the detection system in the device and, for example, whether it can be bypassed.
A personal computer using the Microsoft Windows operating system, (“Microsoft Windows™ PC”) serves as an example of the limitations of the current state of the art. In the Microsoft Windows™ PC, the detection system might be resident in the licensed player for a content protection system (CPS) that can be referred to as CPS-A. That player might be configured as the default player for optical disc types S, H and V. If a disc of any of these three types is inserted into the PC optical disc drive, Windows™ will cause the default player for that particular type of disc to be launched—in this case, the licensed player. Upon launch, the detection system attempts to detect the watermark and, if detected within the allowed usage (as it should be), the licensed player plays the content.
However, CPS-A might only be used on disc type H. Therefore it is only necessary to have the licensed player be the default player for type H. The user may therefore choose to set the default to player for types S and V to be a player that is not licensed under CPS-A watermark detection system. By doing so, disc types S and V are no longer screened for the watermark, and will play the disc regardless of whether the watermark is present. Because Windows™ is an open operating system, there is no way to prevent a user from changing the default player for disc types S and V. If that is done, the effectiveness of the detection system is effectively nullified.